The field of the invention generally pertains to heaters and heating systems. The invention relates more particularly to a secondary heating system which prevents the freezing of static water present in an instant water heater, wherein a temperature-sensitive switch monitors the temperature of a designated area or space and activates a secondary heating element when the monitored temperature falls below a threshold level.
Various types of water heating systems have been developed to provide hot running water in homes, commercial buildings, and the like. One notable innovation in water heating has been the advent of instant water heaters which heat water on demand independent of a centralized water heating system. Such instant water heaters are typically small, electrically operated, and self-contained units which are interposed in water lines near the spout ends, e.g. a faucet. Because of the close proximity between the instant water heater and the spout end, conductive heat loss through the piping is substantially reduced. Moreover, because the primary heating unit of an instant water heater is typically activated only during flow conditions, i.e. when a valve is opened at a spout end, energy is conserved when not in use. One example of an instant water heater of this type is marketed under the trademark, xe2x80x9cHotmanxe2x80x9d by Acorn Engineering in Chino, Calif.
However, it has been observed that when used in cold climates, the water remaining in a conduit portion (see 22 in FIG. 1) of such instant water heaters can freeze when the temperature falls to freezing levels. Although the conduit portion is sheltered within the housing, it is typically not additionally insulated, as is commonly provided for traditional hot water lines. Moreover, because the housing body is typically constructed from a metallic material, such as aluminum, the inner housing temperature can quickly reach levels of the outside ambient air. It is also appreciated that while continuous operation of the primary heating unit alone would prevent freezing, the high efficiency and energy cost savings provided by an xe2x80x9con-demandxe2x80x9d heating system would be lost.
Thus, it would be advantageous to provide a low-power secondary heating system which prevents water remaining in the instant water heater from freezing under static, no-flow conditions. Moreover, it would be beneficial to automate activation of the secondary heating system by monitoring the temperature of a designated area or space, and activating the secondary heating unit when the monitored temperature falls below a threshold level. In this manner, the instant water heater would be available for service at all times, and under all temperatures and climates, while minimizing energy consumption.
It is an object of the present invention to provide a simple secondary heating system which is utilized in conjunction with an instant water heater of the type having a primary heater which is activated only during flow conditions, with the secondary heating system preventing water within the instant water heater from freezing during static flow conditions.
It is a further object of the present invention to provide an automated secondary heating system which monitors the temperature of a designated area or space, such as the ambient temperature outside of the instant water heater, and activates a secondary heating unit when the monitored temperature falls below a threshold value.
A still further object of the present invention is to provide an efficient, low-power secondary heating system which requires substantially less energy than the primary heater of the instant water heater.
It is a still further object of the present invention to provide a secondary heating system which comprises a simple electrical circuit utilizing common electrical components, for facilitating manufacture and assembly.
The present invention is for an antifreeze system for use with an instant water heater of the type having a housing body which encloses a housing volume, a water conduit mounted within the housing volume with an inlet and an outlet, and primary heater means for heating water in the water conduit when water flows therethrough from the inlet to the outlet. In a first preferred embodiment, the antifreeze system comprises secondary heater means for heating the housing volume to prevent water from freezing in the water conduit, and a temperature-sensitive switch operatively connected to the secondary heater means, for switching on the secondary heater means when a monitored temperature falls below a threshold value. And in a second preferred embodiment, the antifreeze system comprises secondary heater means positioned within the housing volume for heating the water conduit to prevent water from freezing therein, and a temperature-sensitive switch discussed above.
Furthermore, the present invention is for an improved instant water heater having a housing body which encloses a housing volume, a water conduit mounted within the housing volume with an inlet and an outlet, primary heater means for heating water in the water conduit when water flows therethrough from the inlet to the outlet, secondary heater means for preventing water from freezing within the water conduit, and a temperature-sensitive switch operatively connected to the secondary heater means, for switching on the secondary heater means when a monitored temperature falls below a threshold value.